FeAl-based coatings deposited by high-energy micro-arc alloying process for wet-seal areas of molten carbonate fuel cell

The corrosion of bipolar plates is a great obstacle to the industrial application of molten carbonate fuel cell (MCFC). No electrical conductivity is needed for the wet-seal materials, thus the application of aluminum coatings is a very effective method to inhibit the corrosion of wet-seal areas of MCFC by the formation of a protective Al2O3 scale. In this work, a high-energy micro-arc alloying (HEMAA) process is attempted to prepare FeAl coatings on the type 316 stainless steel (316SS) as wet-seal material of MCFC using an FeAl intermetallic compound rod as the deposition electrode. The microstructure of the FeAl coatings is analyzed, and its corrosion behavior in molten (0.62Li, 0.38K)2CO3 at 650°C in air is examined by electrochemical impedance spectroscopy. The experimental results indicate that the FeAl coating on 316SS is microcrystalline, with a metallurgic bonding with the substrate. The Nyquist plots for the corrosion of both the bare and the coated steel are all composed of double capacitive loops, but with significantly larger impedance values observed for the coated steel. The FeAl coatings increase greatly the corrosion resistance of 316SS by forming a compact and adhesive Al2O3 scale. ► FeAl coatings for wet-seal materials of molten carbonate fuel cell were studied. ► High-energy micro-arc alloying process was employed to prepare FeAl coatings. ► FeAl coatings are microcrystalline, with a metallurgic bonding to the substrate. ► FeAl coatings have significantly larger impedance values than 316 stainless steel. ► FeAl coatings increase greatly the corrosion resistance of 316 stainless steel.